Before downloading check out the full hardware and software requirement of SharePoint Server 2016 IT preview here.

Few new features are there in the SharePoint Server 2016 preview like:
- Look and Feel
- Mobile usage improvements
- New APp LAuncher
- Simple Share Option (Easily Share your site with users)
- Large file support etc
Check out more on: SharePoint Server 2016 new features

Some of the features are also removed or deprecated, check out this article for more information on SharePoint Server 2016 features deprecated or removed,